Unloading device for motors.



R. B. WILLIAMSON.

UNLOADING DEVICE FOR MOTORS.

APPLICATION FILED APR. so, 1909.

1,017,939. Patented Feb. 20, 1912.

WAX/mom I /WDGMXO/v 79%; 26, v g M UNITED. STATES PATENT cam-on.

ROBERT B. WILLIAMSON, 0F MILWAUKEE, WISCONSIN, ASSIGNOR TO ALLIS-CHALMEBS COMPANY, A CORPORATION OF NEW JERSEY.

UNIOADING DEVICE FOR MOTORS.

Specification of Letters Patent.

Patented Feb. 20,1912.

Application filed April 30, 1969. Serial No. 493,120.

and State of Wisconsin, have invented cer-- tain new and useful Improvements in Unloading Devices for Motors, of which the following is a full, clear, and. exact specification. 7

My invention relates to unloading devices for motors, especially electric motors driving fluid pumps. 2 1

In driving air compressors or other pumps by electric motors, the motors draw "several times the normal full load current from the line during starting if the pump or com pressor is connected to the fluid reservoir. This is very objectionable, especially when the pumps and motors are of a large size. In order to avoid this excessive current, arrangements have been. proposed for allowing the pump-driving motors to run unloaded for a predetermined time after their circuits have been closed.

It is the object of my invention to provide those driving pumps, which is both simple and inexpensive, but withal reliable and'eflicint. which the unloading device for the motor and the pump is automatically operated mechanically by the closing of the switch in the circuit of the motor; and is automatically rendered inoperative some time later.

'The various novel features of my invention will be apparent from the specification and drawings and will be particularly pointed out in the claims.

The singl figure of the drawing shows diagrammatically one embodiment of my invention.

-The motor 10 drives the pump or pumps 11 to supply air to the reservoir 12. The motor may be of any desired type. It is here shown as a three-phase induction motor. The pump or pumps 11 may also be of any desired type, single or double acting.-

They are here shown as single acting air compressors.

As the pressure in the reservoir 12 falls, the diaphragm 13 of the pressure governor 14 is forced upward by the spring 15 until the minimum for which the governor is adjusted is reached, when the upper end of I have provided anarrangement in the, spring 16 will have been moved far enough to theright by the bell-crank lever 17. tocause the switch 18 to snap in a counter-clockwise direction about its fixedpivot 19 to closed position. The closing of the switch 18 admits current from the mains a-bc to the motor 10. The switch lever 18 carries the cylinder of a dash pot 20, the piston of the dash-pot bein connected to the lever 21 carried by the %x'ed pivot. 22, and the lever 21 in turn being connected by links to two levers 23 pivoted at'24 and 25 respectively and carrying rods 26. Through this connection the closing of the switch 18 raises the-rods 26' to lift the inlet valves 27 of the air-compressor from their seats, acting against the adjustable spring 28. Immediately upon the closing of the switch 18, 1

however, the spring 28 begins to raise the piston of the dash-pot 20 to allow .the rods The rate at which this action takes place may be adjusted in any desired 26 to fall.

manner,.as by an adjustable bypass 29 connectmg the 'two ends of the cylinder of the dash-pot 20. The bypass 29 and the-spring 28 are so adjusted that the motor 10 and pumps 11 have practically ,gotten up to speed by the time the rods 26 are 'movedout of engagement'with the inlet valves 27, and the latter are permitted to perform their regular function as inlet valves of the compressor. This arrangement permits the motor to start practically without load, and prevents it from drawing any excessive currentfrom' theline.

-As the compressor operates and the pressure in the reservoir 12 increases, the, diaphragm 13 of the pressure governor 14 'is moved against the Spring 15 until the maximum for which the governor is set is reached. Then, the upper end of'the spring 16 having been properly moved to the left by the'bell-crank lever 17, the switch 18 is opened with a snap action, thus cutting off the supply of'current to the motor 10. This movement of the switch 18 does not affect the rods 26 of the spring 28, for the;valve 30in the dash-pot piston permits the dashpot cylinder to slide rapidly upward without moving the piston.

When the pressure again falls to a minimum, the operation above described is repeated.

Many modifications may be made in the Elli lid

:in the reservoir for controlling precise arrangement here shown and described, and all such which do not, involve a departure from the spirit and scope of my invention I aim to cover in the-following claims,

What I claim as new is 1. In combination, a motor, a pump driven thereby, means controlling the supply of power to the said. motor, unloading means for the pump, and. a mechanical connection between said power-controlling means and said unloading means whereby the operation of the former to admit power to themotor operates the latter to unload the pump.

2.. ln combination, a motor, a pump driven thereby, a reservoir supplied by'the pump, means automatically controlled in response to the amount of the fluid in the reservoir for controlling the supply of power to the motor, normally inoperative unloading means for the pump, and a mechanical connection between said unloading means and said power-controlling means whereb the movement of the latter to power-admitting position, renders the former operative.

3, In combination, motor, a pump driven thereby, a reservoir supplied by said pump, means controlled by the amount oi the fluid I the supply of power to the motor, means for unloading the pump, said unloading means being biased to inoperative position, and a slowly yieldable mechanical connection. between the power-controlling means and the unloading means whereby the operation of the former to admit power to the motor operates the latter to unload the pump for a predetermined time after power is admittted to-the motor..-

l, In combination, an electric motor, a pump driven thereby, a-reservoir supplied by said pump, a switch inthe motor circuit and responsive to the iiuid pressure in the reservoir, unloading means for the pump, and a mechanical connection between the switch and the unloading means whereby the latter is operated by the closing of said switch;

5., in combination, an electric motor, a pump driven thereby, a reservoir supplied by said pump, a pressure switch in the motor circuit responsive to the fluid pressure in the reservoir, means for unloading the pump, said unloading means being biased to inoperative position, and a slowly yieldable mechanical connection between said switch and said unloading means whereby the closing of said switch renders the unloading means operative,

6. in combination, an electric motor, air compressor driven thereby, a reservoir supplied by said compressor, a pressure switch in. the motor circuit respo" ive to the fluid pressure in said reservoir, ans for unloading the compressor, and mechanical connection. between said. pressure switch and said unloading means whereby the latter is mechanically operated by theclosing of said switch. i p

7. In combination, an electric motor, an air compressor driven thereby, a reservoir supplied by said compressor, a pressure switch in the motor circuit responsive to the fluid pressurein said reservoir, means for unloading the compressor," said unloading means being biased to an inoperative position,-and a slowly yieldable mechanical connection between said pressure switch and said unloading means whereby the latter is mechanically operated by the closing of said switch and is automatically rendered inoperative a predetermined time thereafter.

'8. In combination, an electric motor, an. air compressor driven thereby, a reservoir supplied by said -co1npressor, a pressure switch in the motor circuit controlled by the pressure in. said reservoir, means for unloading. said compressor, said means being biased to an inoperative position, and a mechanical connection between said unloading means and said switch, 7

9.,In combination, an electric motor, an air compressor driven thereby, a reservoir supplied by said compressor, a pressure switch intnemotor circuit responsive to the fluid pressure in said reservoir, means for unloading the compressor, a slowly yieldable mechanical connection between said pressure switch. and said unloading whereby the latter is mechanically moved to an operative position by the closi of said switch, and means for automation, causing the yielding of said mechanical connection to render said unloading means inoperative a predetermined time thereatteia 10. in combination, motor, a pump driven thereby, a reservoir supplied. by said pump, means controlled y the amount of the fluid in. said reservoir for controlling the supply of power to the motor, normally inoperative means ior unloading said. pump,- and a mechanical connection between said power-controlling means said unloading 7 means for moving-the latter to an operative position by the movement of said power controlling means to power admitting position.

11. In combination, electric motor driving a load, switch admitting current to the motor, means for unloading the motor, said means being normally inoperative, a mec nical connection bet ,en said switch and aid unloading means tor render mg the latter operative n,

switch. in.

10H the closing of dmitti current ing means for rendering the latter operative for a predetermined time upon the closing of said switch.

13. In combination, an electric motor driving a load, a switch in the motor circuit,

means for unloading the motor, a slowly yieldable mechanical connection between said switch and said unloading means for rendering the latter operative upon the 0103- ing of the switch, and means for causing the yielding of said connection to render said unloading means inoperative a predetermined time after the switch is closed.

14. In combination, an electric motor driving a load, an automatically controlled switch for making and breaking the motor circuit,

means for unloading the motor, said means belng blased to inoperative position, and a mechanical connection between said switch and said unloading means for rendering the latter operative upon the closing of the switch, said mechanical connection including a device which yields to render the unloading means inoperative after a predetermined time after the closing of the switch.

In testimony whereof I afiix my signature, in the presence of two witnesses.

ROBERT B. WILLIAMSON.

Witnesses:

H. 0. CASE, CHAs. L. BYRON. 

